Conversely, the mean and median effect sizes for the N = 30 resamples where the lesion-deficit mapping did not reach statistical significance (i.e. roughly 63%) were 0.07 and 0.06 (range = 0.00–0.16); see Table 4 for similar findings when N = 60.
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The impact of sample size on the reproducibility of voxel-based lesion-deficit mappings.
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The sentences
The results show (1) how often small effect sizes in a heterogeneous population fail to be detected; (2) how effect size and its statistical significance varies with sample size; (3) how low-powered studies (due to small sample sizes) can greatly over-estimate as well as under-estimate effect sizes; and (4) how large sample sizes ( N ≥ 90) can yield highly significant p values even when effect sizes are so small that they become trivial in practical terms.